1. Field of the Invention
The present invention relates to the improvement of a permanent magnet type rotating electrical machine and the system using it.
2. Description of Prior Art
In a permanent magnet type rotating electrical machine with stator winding formed on the stator in distributed winding method, it is possible to bring the induced voltage waveform closer to sinusoidal waveform by improving the stator wiring layout and to reduce distortion rate. However, in the permanent magnet type rotating electrical machine with stator wiring formed on the stator in concentrated winding method, it is not possible to improve wiring layout on the stator.
The Japanese Patent Laid-Open Application No. Hei 06-189481 (JP A 06-189481) discloses that multiple slits are formed on the outer periphery of the magnet storage hole to improve punching work of a thin steel plate constituting the armature core and to reduce the circumferential leakage of magnetic flux. The Japanese Patent Laid-Open Application No. Hei 11-252840 (JP A 11-252840) discloses that slots are installed between the outer periphery of the rotor and the embedded magnet in order to create magnetic resistance, thereby preventing magnetic flux on the horizontal axis. However, these disclosures do not include any description of wiring on the stator side.
A permanent magnet type rotating electrical machine with stator winding formed on the stator in distributed winding method is disclosed in the Japanese Patent Laid-Open Application No. Hei 05-103453 (JP A 05-103453). According to this disclosure, in a salient pole type brush-less d.c. motor, holes are formed at positions corresponding to 60 and 120 degrees in terms of electric angle of the salient pole to remove the cogging torque of the permanent magnet type rotating electrical machine. Furthermore, the Japanese Patent Laid-Open Application Nos. Hei 09-163647 (JP A 09-163647), Hei 10-178751 (JP A 10-178751), Hei 10-285845 (JP A 10-285845) and Hei 10-285851 (JP A 10-285851) disclose that, in a permanent magnet type rotating electrical machine with stator winding formed on the stator in distributed winding method, a slit or narrow portion is formed between the outer periphery of the rotor and permanent magnet.
Problems to be Solved by the Invention
When the rotating electrical machine according to the prior art is used in a drive system or power generation system, problems still remain in reducing vibration and noise and in improving efficiency.
An object of the present invention is to provide a permanent magnet type rotating electrical machine and a system using such a machine characterized by reduced vibration and noise and improved efficiency.
Means for Solving the Problems
In a drive system, a big vibration noise may occur to the rotating electrical machine and characteristics are deteriorated. And such problems as heat generation, reduced efficiency and deteriorated characteristics may occur to a power generation system. These problems are considered to be caused by an excessive waveform distortion rate of the induced voltage in the permanent magnet type rotating electrical machine. As a result, harmonic wave current flows to the rotating electrical machine so that pulsation torque, vibration and noise are increased or efficiency and characteristic is deteriorated.
One of the characteristics of the present invention is found in that, in a permanent magnet type rotating electrical machine comprising;
a stator with concentrated winding provided on the tooth of the stator core, and
a rotor with permanent magnets embedded therein;
two flux barriers extending in the axial direction are provided for each magnetic pole of the rotor on the bridge between the permanent magnet constituting a magnetic pole and the outer surface of the rotor at the position where the width of the permanent magnet is divided into three parts in such a way that the ratio of each of both ends and center is 1 to 2 or more. It is preferred that flux barriers made of grooves and holes be formed at an equally spaced interval over the entire outer periphery of the rotor.
In this case, height coefficient C1 is preferred to be defined as 0.2xe2x89xa6C1xe2x89xa60.6 when t=C1.h is assumed, where xe2x80x9ctxe2x80x9d (mm) is the height of said flux barrier as a groove or hole, and xe2x80x9chxe2x80x9d (mm) is the thickness of said bridge. It is preferred that groove width coefficient C2 be defined as 0.5xe2x89xa6C2xe2x89xa61.2 when W2=C2.Wt is assumed, where W2 (mm) is width between the bridge and the adjacent flux barrier of the groove or hole, and Wt (mm) is the width of the tooth of said stator core.
Such an arrangement of flux barriers causes local magnetic saturation on the bridge of the magnetic pole, and the magnetic path is divided into three portions; one big magnetic path at the center and two smaller ones on both sides. As a result, the the waveform of the surface magnetic flux density of the rotor is brought closer to the sinusoidal waveform, thereby reducing the distortion of induced voltage waveform.
Application of this rotating electrical machine to a power generation system or drive system allows high-quality power energy to be generated and supplied, and permits driving force with less vibration or noise to be provided.